How Does A Whole House Fan Work? (*2021 Guide*)

Do you want to find out how whole house fans work?

At Home Inspector Secrets, we’ll give you the down and dirty on how whole house fans work — and if the purchase is worth the hassle.

In this article, you will discover…

  • Exactly how whole house fans work to cool down your home
  • How increasing your attic vents can double the performance of a house attic fan
  • How you can save up to 90% on your A/C costs by using a whole house fan
  • One little-known reason why people love whole house fans, known as “the breeze effect”
how does a whole house fan work

Let’s get started with this guide!

Will A Whole House Fan Cool Down My Home?

The answer to this question is that yes, whole house fans work very well at cooling homes, but only under certain conditions.

According to Kansas State University, a whole house fan is most effective when the exterior air is cooler than your home’s interior, and the outdoor air also has low humidity — more typical of drier climates.

Obviously, if the outdoor air is warmer than the home’s interior air, then the cooling effect will be almost non-existent…though the “breeze effect” may still be nice on the skin.

A whole house exhaust fan works by exhausting the stale and warm interior air to the outside through the attic vents such as the ridge, gable, and passive vents.  The whole house fan will then pull in fresh outdoor air into your home to quickly cool the entire house.

When To Use A Whole House Fan?

The most common times to use a all house fan is during the early morning and in the evening because as the sun goes down, the air dramatically cools..

Some homeowners like to just turn on the whole house fan for 30 minutes or so in the evening, and this is enough to keep them cool for the entire night. Other users like to keep the whole house fan on during the entire night.

Leaving the whole house fan on all night will help keep the home cool for the next day, and it will delay the need for using the expensive air conditioner, or may even eliminate the need for it.

If you run the whole house fan during the entire night, you may want to put it on the low speed setting in order to minimize noise and energy usage.

My favorite whole house fan is the QuietCool Whole House Fan.

QuietCool Whole House Fans are hung from the attic rafters which makes them much more quiet, and they also have automatic dampers to minimize air leakage.

You can view the price of QuietCool Whole House Fans on Amazon here.

How Do I Get The Most Performance Out Of A Whole House Attic Fan?

According to the U.S. Energy Department, the best way to improve the performance of a whole house fan is to increase your attic ventilation. Most attics will have a combination of soffit, ridge, and gable ventilation (as well as single unit passive vents).

This makes sense because a whole house fan is expelling the warmer interior air to the outside through the attic vents.And if there isn’t enough attic venting, then this greatly slows down the rate at which the air is moved to the outside.

Not enough attic venting will put strain on the fan, causing it to use more energy, and the cooling effect will take much longer.

This is why it would be better to have a less powerful whole house fan (a lower CFM rating) but with much more attic venting — compared to the opposite — a very powerful fan but with less attic vents.

In addition, installing more attic venting is relatively cheap compared to the cost and installation of a whole house fan.

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Open Windows For A Whole House Fan To Work Properly

In addition to increasing your attic venting, it is important to open an adequate number of windows or doors. Whole house fans create a negative pressure on the interior of the home, while exerting a positive air pressure inside the attic.

You need enough intake air for a whole house fan just like for attic fans, except the intake air is through windows and doors.

If there isn’t enough openings for fresh outdoor air to be pulled into the home, then the whole house fan is going to work much harder, and won’t be nearly as effective.

Use Ceiling Fans For More Home Cooling

The U.S. Energy Department also recommends using ceiling fans together with a whole house fan in order to get the most cooling for your home.

Read Also: How To Use Whole House Fans

how does a whole house fan work (ventilation)

Is A Whole House Fan Faster Than A Traditional A/C?

The best whole house fans are significantly faster than a traditional air conditioner because an A/C system does not expel any of the warm interior air to the outside.

A whole house fan is similar to when you first enter a car on a very hot day. What is the first thing you do? You open the windows, and blast on the A/C. The A/C “pushes” out the hot air to the outside, and replaces it with cooler air.

With a traditional home A/C this process can take a while because it isn’t connected to the exterior.

How Much Can I Save With A Whole House Fan Installation?

The typical whole house fan is about 70-90% cheaper than a traditional split system air conditioner.

While an average 3 ton air conditioner may use up to 3500 watts, a whole house fan may use only 100 watts which is about 35 times less energy.

Can I Use The Whole House Fan When It Is Warmer Outside?

Yes, you can still use a whole house fan when it is the same temperature as the outside or even warmer, and there are even other benefits besides cooling.

For one, using a whole house fan for a few minutes before you turn on your air conditioner will greatly speed up the cooling effect of your traditional A/C if you decide to use it. This works by expelling all of the hot air in your home which your A/C cannot do.

After you have expelled all of the warm interior air, then you can turn on the A/C and it will cool down the home much faster.

how does a whole house fan work

Are There Other Advantages Of A Whole House Ventilation Fan Besides Cooling?

A Nice Ventilation Benefit — The Breeze Effect

In additional to helping your A/C, if the outdoor air is the same temperature or even a little warmer, you can still benefit from the “breeze effect” of your whole house fan.

It would be similar to having an outdoor ceiling fan on a porch. Even though it isn’t pulling in cooler air, you will still feel cooler because of the breeze just by itself.

This phenomenon is known as evaporative cooling.

Remove Pollutants

Besides the breeze effect, another benefit of a whole house fan is that it removes pollutants from your home such as radon gas, formaldehyde, cooking fumes, and other harsh chemicals.

Especially with today’s modern homes, our houses are designed to be ultra air tight and energy efficiency.

The problem with a house being air tight is that it also tends to capture bad fumes and harsh chemicals. For some homeowners, this reason alone may be enough to invest in a whole house fan.

Read Also: How To Use A Whole House Fan

The Bottom Line — Do Whole House Fans Really Work?

In my opinion, as a licensed home inspector, is that whole house fans can be a great investment for your home, and definitely be worth the expense. However, it isn’t always a one-sized fits all solution. In dryer climates, whole house fans tend to be much more popular than in the humid northeast.

In addition, older model whole house fans can also be noisy, and much less efficient that newer whole house fan models such the Quiet Cool whole house fans. But there are even ways to make a whole house fan quieter such as by using rubber seals, and even building a platform above the ceiling joists.

Regardless, it’s a good idea to considering adding a whole house fan for your home comfort.

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8 thoughts on “How Does A Whole House Fan Work? (*2021 Guide*)”

  1. Forgive my lack of knowledge but I didn’t see this question answered. What about the colder seasons? Since cold air drops, would cold air from the attic drop through the fan and make the furnace run even more in the fall and winter months; to keep the inside temps warm?

    Reply
    • Hi Mark,

      Yes, this is a common issue with WHFs. Many WHF users build insulation boxes to cover their WHF during the cold season. Some WHFs already come with insulated dampers that will prevent cold/air infiltration.

      Cheers,

      Arie

  2. Hello Arie,
    I recently got a phone quote for a fan, and during the salesperson’s spiel, she said that the positive air pressure created in the attic also cools the attic, which then provides an additional buffer on hot days. The idea is that the insulation gets “saturated” with heat, and the cool air being blown into the attic pushes that heat out.

    I have not found a similar assertion on the web. Do you know if this is true?

    Second, unrelated question. Our attic has maybe 22″ of vertical space – too low for a fan to be installed. However, we do have a 9′ ceiling in the garage. What are your thoughts on installing it *below* the ceiling in the garage?

    Thanks!

    Reply
    • Hey Matt,

      The salesperson was correct in a sense because you get the same benefit as installing an attic fan as you do a whole house fan — you remove the attic heat radiating downward towards the home’s interior. It is the same idea as when you leave a car out in the sun with the windows up, the heat can build up to an enormous temperature. But in addition to removing the heat in the attic, you also ventilate the entire home with (hopefully) cooler outdoor air.

      For the second question, whole house fans are usually installed on the highest level (hot air rises) and towards the center of the home. If your home is only one level, then installing the whole house fan in the garage ceiling could work. You will have to keep the garage interior door open and will have to open a window (or crack open the garage door) in order for it to work. I would probably look at some other options though because you aren’t supposed to leave the garage interior door open since it is a fire hazard. Fires usually start in the garage which is why some building codes require auto-closing garage interior doors.

      Good luck!

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Arie Van Tuijl

Arie Van Tuijl

I am a licensed home inspector in two U.S. states and the founder of Home Inspector Secrets. After performing hundreds of inspections, and seeing thousands of house defects, I realized people would love to have an online resource dedicated to home maintenance. I write detailed home guides and product reviews sprinkled with inspection tips. You can read my bio here.

About Home Inspector Secrets

Home Inspector Secrets is an online resource for owners, buyers, and sellers to understand all aspects of home maintenance. We have detailed home guides, product reviews, inspection advice, and much more.

Other Home Guides

Looking to learn more about home maintenance? Check out our other informative home product reviews and guides!